This invention relates to an gas blower and a method for discharging gas from a blower, and more, particularly, to such a blower and method having an improved air discharge pattern.
Rotary positive blowers have long been used in the art for receiving a gas, such as air, compressing it and discharging the compressed air for use externally.
Several designs of rotary positive blowers include a housing having an inlet plenum and an outlet plenum respectively registering with an inlet opening and an outlet opening respectively formed in opposed walls of the housing. The inlet plenum receives ambient air and introduces into the housing, and the outlet plenum receives the pressurized, or compressed, air and discharges it for further use.
Many of these designs include two "figure eight" impellers disposed in the housing and mounted on vertically-spaced, parallel shafts mounted for rotation in the housing in opposite directions. The shafts extend generally perpendicular to the flow path of air though the housing, as each impeller passes the inlet opening, it traps a definite volume of air and carries it around the housing to the outlet for discharge.
However, due to the difference between the pressures of the trapped volume of air and the discharge plenum, a sudden rush of air into the trapped volume of air occurs when an impeller passes the outlet opening. This rush of air causes shock, vibration, pulsation and noise, all of which are highly undesirable.
In order to minimize these disadvantages, the assignee of the present application has marketed an improved blower design under the "Roots Whispair" trademark. According to this design, jet openings are defined in the outlet plenum to recirculate some of the air from latter area back to the area of the housing that receives the impellers and the incoming air is trapped by the impellers simultaneously with the discharge of the pressurized air. This causes a gradual equalizing of the pressure of the trapped air and the pressure in the discharge area and reduces the shock, vibration, pulsation and noise caused by the conventional blowers discussed above.
Although this latter design has been eminently successful, there is still room for improvement. For example, there is an abrupt change in the discharge flow area which causes sudden changes in the discharge air velocity and results in turbulances, which, in turn, cause added pressure drop and noise.